No evidence of a lower visual field specialization for visuomotor control

The lower visual field (loVF) has been hypothesized to demonstrate specialization for skilled, visually guided action. According to Danckert and Goodale (Exp Brain Res 2002; 137: 303-308), this visual field asymmetry indirectly suggests that the loVF has privileged connections to visuomotor networks within the dorsal visual pathway. Here we attempted to replicate the loVF advantage during the execution of a discrete aiming movement to targets of various widths (index of difficulty ranging from 1.5 to 5 bits). In addition, we employed trials in which vision of the target object was available or unavailable during the reaching movement to determine whether or not the purported visual field asymmetry reflects enhanced central planning (i.e., feedforward) or online control (i.e., feedback) processes. Reaching trajectories were examined for indicators of online amendments, and movement times and endpoint characteristics were examined to quantify possible visual field asymmetries in relative speed/accuracy trade-offs. In terms of reaching kinematics, it was found that vision of the target during the reaching movement resulted in greater online control of the reaching trajectory; however, no significant main effects or interactions involving visual field were observed. In other words, fixating in the upper or the lower region of peripersonal space did not influence the nature of reaching control (i.e., feedback vs. feedforward). Most importantly, our movement time and endpoint accuracy data elicited a robust speed/accuracy trade-off in both upper and lower regions of working space [cf. Fitts, J Exp Psychol 1954; 48: 303-312]. Thus, and contrary to previous findings (such as those reported by Danckert and Goodale), the indices of difficulty coupled with the discrete aiming task used here did not elicit a lower visual field advantage for visually guided action.